3/4" or 1/2" to shower valve vacinity

I'm in the planning stages for a new double shower and am currently thinking water supply. It's a ranch style with concrete slab. The nearest current stub outs are 16 feet away (8' across the loft and 8' down the wall). There are 3/4" stubs and 1/2" stubs available to me at pretty much the same location
Should I pull 3/4" as near to the control valve as possible and then reduce to 1/2" or just take the 1/2" from the stub and run it all the way?

When I did my kids bathroom bath/shower I used 1/2" copper for an approximate 8' length. Although the flow is fine, I did end up with a high pitched whine when in use. I read somewhere and believe this might be due to a combination of the smaller 1/2" pipe and a small protrusion of solder forming on the inside of the pipe as it turns 90 deg into the valve (not sure whether it is the cold or hot side). Only a theory since I really can't explain the phenomena. It's been there for many years so it can't be residual air in the pipe.

When I did my master bathroom I ran 3/4" all the way up to the shower valve with no similar problem. The master bath also has two other valves for an overhead shower and a rear mounted shower. One side benefit is that there is less pressure drop in 3/4" pipe vs 1/2". However for 8' that difference is very small.

In any case, I may be wrong to blame the pipe size but if I had to do it over again I’d run ¾” in the kids bath/shower.